Experience shows that most failures of electronic components occur at the interfaces between devices, rather than in the interior of the devices. This tends to be true irrespective of whether the device is an integrated circuit chip, a printed circuit board or a system unit. The interfaces between devices include drivers, solder pads, pin connectors and backplane wiring in appropriate cases. These components tend to operate hotter than other components because of the need to carry higher interface signaling currents. Connecting pads on integrated circuits and connecting pins have always been a major source of unreliability. Interface wiring, backplane wiring and the like are often exposed to physical damage from any number of sources.
One known way to increase the reliability of a system is to use triple modular redundancy (TMR) of system devices and to vote on the correct result between the devices. For example, it is known to provide three or more devices, each doing the same thing, and to compare the results from each to detect failures. It is also known to provide TMR in the interface circuits of such devices. For example, it is known to provide three or more sets of signaling drivers, pins, etc. between chips, boards and units. However, such techniques are seldom used because of the expense required for the additional redundancy.